Poco

This plugin installs a widget for showing a Google Calendar agenda on the sidebar. 
Once installed it adds a sidebar widget called ‘Google Calendar’ that may be dragged into your sidebar. 
Each widget can be configured with a ID of the calendar feed, a title, and the number of agenda items to show.
The calendar feed ID is the ID next to ‘Calendar ID:’ in the Google Calendar settings.
Multiple widgets can be used on the same page and each one can reference a different feed.
See also <a href="http://notions.okuda.ca/wordpress-plugins/google-calendar-widget/" rel="nofollow ugc">http://notions.okuda.ca/wordpress-plugins/google-calendar-widget/</a>

Google Calendar Widget

This plugin installs a sidebar widget that can show the upcoming events from a Google Calendar feed.

MDJM

Google Calendar Sync is an essential extension to the MDJM Event Management plugin.
You’ve automated so much of your events business, and yet you’re still manually updating your calendar to ensure you do not double book, or worse still, forget about the booking.
And what about event changes? Some event details can change multiple of times during the lead up to the event itself. Are you manually updating your calendars each and every time?
With the MDJM Google Calendar Sync extension, all of this is now taken care of for you, leaving you to concentrate on more revenue generating activities for your business.
Key Features
<ul>
<li>Automatically synchronises new events to your calendar</li>
<li>Automatically updates existing events changes to your calendar</li>
<li>Allows you to select which event status’ should be synchronised</li>
<li>Supports content tags for custom calendar titles, descriptions and venue addresses</li>
<li>Per event reminder settings</li>
<li>Retrieve event alerts via email and/or by on screen popups</li>
<li>Fully integrated with the official Google API library</li>
</ul>

MDJM Extension – Google Calendar Sync

Automatically adds your event bookings to your Google calendar and keeps them up to date.

Google Calendar Widget vs MDJM Extension – Google Calendar Sync